The proposed study will investigate how the predictive relationship between autonomic underarousal and later antisocial behavior is affected by additional factors such as the comorbidity of two disorders, social adversity, gender, and ethnicity. Measures of skin conductance and heart rate taken at age 3 will be compared in four groups of children: hyperactive and antisocial, antisocial only, hyperactive only, and normal controls at ages 8 and 16. It is hypothesized that children who are both antisocial and hyperactive will demonstrate the lowest levels of arousal. This relationship is hypothesized to be consistent across diverse ethnic groups, but stronger in female antisocials and antisocials from benign homes where the social predisposition towards crime will be weaker. The significance of the proposed study lies in the identification of the physiological correlates of a subgroup of antisocial children who are at increased risk for adult offending, which has important implications for early intervention.